Does creating a loom in cables in a system make a significant difference?

I've messed with "high end" cables since the late '80s. Yeah, you can hear a difference. Maybe you shouldn't- that is, the cable is coloring the sound. I dunno. 

One serious guy I know swears by basic old stock Rat Shack and his system is beyond the pale.

I think the one advantage of a "full loom" is that it enables you to hear the "house sound" of that brand/line. Cabling can be tricky if you are trying to use it to compensate. I use very basic stuff in my vintage system- trying to stay close to period. In my main system, I had great success with Kubala-Sosna, which nicely matches the character of my system. But, I can't extrapolate. I will say K-S stepped up when a very long XLR had a bad connector- 17 years later. He replaced it at no cost and no cost shipping back. 

If you do indulge in cable comparisons, you can get a headache. There are some known synergies for people with certain speaker/amp combos. I would start there if that's a question. 

I'd also say, with some experience, that I would rank the importance of cabling low on the priority list if you are building an entire system from scratch. The cables can make a difference but I wouldn't put cart before horse (or something). 

I say if you have crappy cables it's important to have ALL crappy cables for consistency. Also, if you decide otherwise, it's important to use a forum like this to note how you've bought expensive cables and like to be recognized for the serious listener and real smart person you obviously are. Otherwise, what's the point?

I’m one of the lucky guys that doesn’t hear a difference between cables.

I use ’standard’ copper cables all around, does that count as a ’loom’?

I use bi-wiring with my stereo set and bi-amping with my 5.1 set. Couldn’t hear the difference with that either, but hey, the cables were not very expensive.

The "loom" theory is very convenient for manufacturers to promote sales of their own cables. To the extent that cables impact on sound quality there is no more logic in suggesting that the same make of cables throughout a system has an exponential impact on sound quality than there is in suggesting that using components from the same manufacturer does so. I don't recall a "loom" theory being advanced in the latter regard to anything like the same degree as I do for cables.

I now have mostly the same make and model of cables in my system but to the extent that the sound quality of the system has improved, it's because the cables are better - not because they are from the same manufacturer.

I think the "loom" theory might "work" for certain listeners particularly where a cable manufacturer has a particular sonic signature (I would suggest Nordost, for example). In that case where a listener is particularly drawn to that kind of sound, then reinforcing it with more of the same might prove attractive.

+1 @yoyoyaya